256 Feeds and Feeding. 



from 7.06 lbs,, there remains 4.63 lbs., the amount of digestible 

 nutrients Avhieh were required to furnish the remainder of the heat 

 needed to warm the body. Since the energy used in masticating 

 and digesting the ration is also finally changed into heat in the 

 body, the nutrients used for this purpose are not wasted but help 

 in warming the body. Hence the heat generated in the body as a 

 result of the internal work and the work of masticating and di- 

 gesting the ration may be enough to properly warm the body, and 

 no nutrients need then be burned up in the body simply as fuel. 



Feeds such as poor hay, corn stover, and straw, which contain 

 relatively little net energy, are lower in price than concentrates 

 which supply much net energy. It is therefore usually most eco- 

 nomical to formulate a ration for maintenance made up so far as 

 possible of such roughages. So long as 2.43 lbs. of net nutrients 

 are furnished for the upkeep of the body, the other digestible 

 nutrients in the maintenance ration for the 1000-lb. horse may be 

 used up in the work of digesting, masticating, and assimilating the 

 feed. The net nutrients expended in external work and the nutri- 

 ents used up in the work of digestion, mastication, and assimila- 

 tion will then furnish sufficient heat to warm the body. 



394. Minimum protein requirement. — In experiments by Gran- 

 deau and Leclerc,^ 3 horses maintained their weight for 4 or 5 

 months on a ration of meadow hay furnishing an average of 0.54 

 lb. of digestible protein daily per 1000 lbs. live weight, the hay of 

 course containing some amids beside the true protein. One of the 

 horses gained 5 lbs. in 2 months on a daily allowance of only 0.45 

 lb. of digestible protein per 1000 lbs. live weight. In another 

 case an allowance of 0.37 lb. of digestible protein daily per 1000 

 lbs. of live weight proved insufficient to maintain the nitrogen 

 equilibrium. Evidently the minimum protein requirement for the 

 horse ranges from 0.4 to 0.6 lb. per 1000 lbs. live weight, which 

 is the same as that of the resting ox as determined by Armsby. 

 We may therefore hold that about 0.45 lb. of digestible protein 

 constitutes the minimum daily maintenance allowance of that 

 nutrient for the 1000-lb. resting horse. (97) 



395. The nutritive ratio. — We have seen that under normal condi- 

 tions the non-nitrogenous nutrients — carbohydrates and fats — fur- 

 nish the energy necessary for the production of muscular work, 

 and that no more protein tissue is usually broken down during 



^ Warington, London Live Stock Journal. 1884. p. 9. 



